The present invention relates to a method of providing for the testing of programmability and speed of one time programmable read only semiconductor memory cells.
In the past, electrically programmable read only memory cells have been put into packages with light transmitting windows in order to permit them to be erased by exposure to a relatively intense source of ultra violet light. As a part of the normal testing procedure for such devices a pattern is programmed in to verify programming functionality and then a speed check is performed. Next, the part is stamped with the correct speed, erased by ultra violet light and then shipped to the customer. Due to the expense of providing a package for these chips with a transparent window more and more of such EPROMS are being packaged without windows as one time programmable PROMS (Programmable Read-Only-Memories). Such devices can ordinarily not be tested prior to shipment to a customer because once programmed they can not be erased by ultra violet light.
Accordingly, a principal object of this invention is to provide a method of testing arrays of one-time programmable read only semiconductor memory cells after being packaged.